Microwave plasma processing process and apparatus

ABSTRACT

A microwave plasma processing process and apparatus useful in the fabrication of integrated circuit (IC) or similar semiconductor devices, wherein the object or material to be processed, such as a semiconductor wafer, is processed with plasma generated using microwaves transmitted through a microwave transmission window disposed perpendicular to an electric field of the progressive microwaves in the waveguide.

This application is a continuation of application Ser. No. 07/604,343,filed Oct. 25, 1990, which is a continuation of application Ser. No.07/532,234 filed Jun. 4, 1990, which is a continuation of Ser. No.07/416,002 filed Oct. 2, 1989, which is a continuation of Ser. No.07/150,446, filed Feb. 1, 1988; which is a continuation of Ser. No.07/016,513, filed Feb. 17, 1987; and which is a continuation of Ser. No.06/802,332, filed Nov. 27, 1985, all now abandoned.

BACKGROUND OF THE INVENTION

. .1..!. Field of the Invention

The present invention relates to a plasma processing process andapparatus useful in the fabrication of integrated circuits (. .ICS.!..Iadd.ICs.Iaddend.) or similar semiconductor devices, More particularly,the present invention relates to a microwave plasma processing methodand process and an apparatus used for an etching or ashing process inthe fabrication of . .ICS.!. .Iadd.ICs .Iaddend.or similar devices. Thepresent invention enables processing of a material at a higher speed bysignificantly reducing the reflection of microwaves.

. .2..!. Description of the Related Art

In a process for forming fine patterns in . .ICS.!. .Iadd.ICs.Iaddend.or similar semiconductor devices, an etching or ashing processbased on a dry process is widely used. A typical dry etching process isthe plasma etching process. The plasma etching process, as compared withthe wet etching process, which was frequently used at the beginning ofthe IC industry, has various advantages such as fine resolution and lessundercutting, reduction of the number of fabricating processes byelimination of wafer handling for rinsing and drying, etc., and inherentcleanliness: Plasma etching, in particular, makes it possible to performsequential etching and stripping operations on the same machine, makingit possible to have a fully automated fabricating process for . .ICS.!..Iadd.ICs .Iaddend.or similar devices.

A "plasma" is a highly ionized gas with a nearly equal number ofpositive and negative charged particles plus free radicals. The freeradicals are electrically neutral atoms or molecules that can activelyform chemical bonds. The free radicals generated in a plasma, acting asa reactive species, chemically combine with materials to be etched toform volatile compounds which are removed from the system by anevacuating device.

Recent conventionally used plasma etching apparatuses comprise a plasmagenerating region (plasma generating vessel or generator) and a reactingregion (reactor or etching chamber) spaced apart from each other andconnected through a tube or waveguide to guide the microwaves from theplasma generating vessel to the reactor. In these apparatuses, thereactor has a microwave transmission window of silica or ceramicdisposed perpendicular to the flow direction of the microwaves in thewaveguide. The microwave plasma etching apparatus of the above-describedstructure is hereinafter referred to as a "perpendicular incidence-typeplasma etching apparatus".

Examples of the perpendicular incidence-type microwave plasma etchingapparatus can be found in patent literature, such as Japanese ExaminedPatent Publication (Kokoku) Nos. 53-14472, 53-24779, and 53-34461;Japanese Unexamined Patent Publication (Kokai) No. 53-110378, and U.S.Pat. No. 4,192,706, which is a counterpart of Japanese Examined PatentPublication (Kokoku) No. 53-14472.

In the conventional apparatuses, however, the processing rate is low asa result of the reflection of the microwaves at the two interfaces ofthe microwave transmission window. Further, matching of the microwavesis difficult because the microwaves are not effectively transmitted intothe reactor. Furthermore, it is not easy to cool the stage for theobject under processing or to reduce the size of the apparatus.

SUMMARY OF THE INVENTION

We now found that the prior art problems can be overcome if, in themicrowave plasma processing process, we use microwaves transmittedthrough a microwave transmission window disposed perpendicular to anelectric field of the progressive microwaves in the waveguide.

Accordingly, in an aspect of the present invention, there is provided amicrowave plasma processing process in which the material to beprocessed is processed with plasma generated using microwavestransmitted through a microwave transmission window disposedperpendicular to an electric field of the progressive microwaves in thewaveguide.

In another aspect of the present invention, there is provided amicrowave plasma processing apparatus which includes: a microwavegenerator; a waveguide for the progressive microwaves connected with themicrowave generator; a microwave transmission window defining a part ofthe waveguide disposed perpendicular to an electric field of theprogressive microwaves in the waveguide; and a vacuum reactor forprocessing a material, the reactor being partially defined by saidmicrowave transmission window.

In the microwave plasma processing process and apparatus of the presentinvention, microwaves are effectively transmitted through the microwavetransmission window. Therefore, they are effectively introduced into thevacuum reactor in which plasma processing is carried out. No disturbanceof the microwave mode is caused, while, as described above, themicrowave transmission window is disposed perpendicular to an electricfield of the microwaves, i.e., parallel to the direction of the travelof the microwaves in the waveguide.

According to the present invention, it becomes possible to process theobject at a higher processing rate. Further, matching of the microwavesbecomes easy. Furthermore, it becomes possible to easily cool the stagefor the object and to reduce the size of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the present invention will be described below with referenceto the accompanying drawings, in which:

FIG. 1 is a schematic view of a prior art microwave plasma etchingapparatus;

FIG. 2 is a schematic view of another prior art microwave plasmaprocessing apparatus;

FIG. 3 is a partial schematic view of a typical prior art perpendicularincidence-type plasma etching apparatus;

FIG. 4 is an enlarged schematic view of the microwave transmissionwindow and object of the device shown in FIG. 3;

FIG. 5 is a schematic view of a microwave plasma processing apparatusaccording to the present invention;

FIG. 6 is a schematic view of another microwave plasma processingapparatus according to the present invention;

FIG. 7 is a perspective view of the plasma processing apparatus shown inFIG. 6;

FIG. 8 is a schematic view of still another microwave plasma processingapparatus according to the present invention;

FIG. 9 is a perspective view of the plasma processing apparatus shown inFIG. 8;

FIG. 10 is a schematic view of still another microwave plasma processingapparatus according to the present invention;

FIG. 11 is a perspective view of the plasma processing apparatus shownin FIG. 10; and

FIG. 12 is a schematic view of still another microwave processingapparatus according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the preferred embodiments, a more detailed explanationwill be made of the related art, for reference.

Referring to FIG. 1 which is an illustration of the plasma etchingdevice of U.S. Pat. No. 4,192,706, a conventional microwave energysupplying device includes a magnetron power source 12, a waveguide 16, atunnel 17, a plunger 18, an applicator 19, a microwave shield housing20, and a plasma generating vessel 21. Descriptions of these elementsare omitted because the elements are easily understood by those skilledin the art. A reactor 1 is separated from the plasma generating vessel21 by a specified distance. This spatial separation makes it easy toobtain matching between the load impedance (plasma 22) and the outputimpedance of the microwave source 12 (a magnetron) at a frequency of2.45 GHz so that the microwave energy is absorbed effectively by gasplasma 22, and the generating efficiency of an active species (radicals)is increased significantly. The radicals thus generated are introducedinto a reactor 1, where a wafer 9 or other device to be processed ispositioned.

Recently, in order to overcome the problems in the apparatus of theabove-discussed U.S. patent, we invented an improved microwave plasmaprocessing apparatus for removing photoresist films or etching offprotective layers in the fabrication of IC semiconductor devices as wellas an improved microwave plasma processing apparatus having a highprocessing rate and able to use various kinds of reactive gases and thusprevent damage to the IC devices being processed due to the plasma. Thisis set forth in U.S. Pat. No. 4,512,868 issued Apr. 23, 1985. Across-sectional view of the preferred microwave plasma processingapparatus according to that prior invention is illustrated in FIG. 2.

In FIG. 2, the microwave energy having a frequency of 2.45 GHz, suppliedfrom a magnetron (not shown) having a 400 W output power, is transmittedthrough a waveguide 2. A plasma generating vessel 21 is substantially apart of the waveguide 2 and partitioned from the other part of thewaveguide 2 by a ceramic or silica glass, vacuum tight window 29. Adummy load 25 is attached to the end of the total waveguide, namely, thewaveguide 2 including the plasma generating vessel 21, in order toreduce reflected microwave power. The dummy load is water-cooled by awater-cooling pipe 38. As a result, the microwave energy applied to thereactive gas is substantially a travelling wave and ionizes the gasuniformly. A processing vessel (reactor) 3 is coupled to the plasmagenerating vessel 21 through several holes 4 formed in a wall of thewaveguide 2. In the reactor 3, an object or material to be processed 26,such as a semiconductor wafer, is mounted on a platform or stage 27. Theholes 4 act as a shielding means for the microwave energy to prevent theplasma generated in the vessel 21 from intruding into the processingvessel 3 thereby protecting the object 21 positioned inside theprocessing vessel 3. At the same time, the holes 4 act as a transmittingmeans for the radicals. The plasma generating vessel 21, the processingvessel 3, and a pumping device (not shown) comprise a vacuum system, andthe system is evacuated through exhaust tubes 6. A reactive gas is ..introducted.!. .Iadd.introduced .Iaddend.into the plasma generatingvessel 21 through a gas feeding tube 5, and ionized to form a plasma.Radicals generated in the plasma pass through the holes 4 to reach theobject 26 in the processing vessel 3 and react with the object 26forming volatile compounds which are exhausted by the vacuum pump. Thedistance between the plasma generating vessel 21 and the object 26 isapproximately 0.8 cm. This length of 0.8 cm is equal to the distancewhere the plasma may intrude if the shielding means of plasma, ortransmitting means for the radicals is taken away. The dimension of theplasma generating vessel 21, in the direction of the microwave electricfield, is slightly reduced from that of the original waveguide 2, by 8mm for example. The reduction in the dimension intensifies the microwaveelectric field inside the plasma generating vessel 21 thereby increasingthe plasma generating efficiency.

Utilizing the apparatus of FIG. 2, as described above, several plasmaprocessing experiments were performed, using a reactive gas mixture ofO₂ +CF₄. The mixing ratio of CF₄ was 20% and its pressure inside theplasma generating vessel 21 was 0.5 Torr. The output power of themagnetron was 400 W. A number of silicon wafers of 4 inches in diameterhaving photoresist layers on them were processed, resulting in a higherashing rate of 1.5 times that obtained with a conventional plasmaprocessing apparatus. In this experimental processing, ashing of thephotoresist layers was satisfactory. The photoresist material attachedto a undercut portion or back side portion of the wafer under processingwas completely removed. In addition, no damage to the wafer was foundand the protection of the wafer was found satisfactory.

However, in this perpendicular incidence-type plasma etching apparatus,there are several problems. These are explained with reference to FIG.3, which is a simplified illustration of the perpendicularincidence-type apparatus, and FIG. 4, which is an enlarged illustrationof the microwave transmission window of FIG. 3.

As is illustrated in FIG. 3, the microwaves are guided through awaveguide 13, which is connected with a microwave power source (notshown). A reactor or etching chamber 14 is provided with a reactive gasinlet 11 and an evacuation outlet 15, connected to a conventionalevacuation system (not shown) to form a vacuum in the chamber, and isconnected with the waveguide 13 through a microwave transmission window10 of silica or ceramic disposed perpendicular to the flow direction ofthe microwaves. An object 8 or material to be processed, such as asemiconductor wafer, is mounted on a stage (not shown; reference number7 in FIG. 4) and is disposed in the reactor or vacuum chamber 14.

It is apparent from FIG. 4 that the microwaves perpendicularly incidenton the microwave transmission window 10 are partially reflected at twoportions. First, as is shown with an arrow R₁, the incident microwavesare partially reflected at an interface between the air or otheratmosphere inside the waveguide and the ceramic or silica window.Second, the microwaves penetrating into the window are partiallyreflected at an interface between the window and the vacuum or plasma ofthe reactor. In addition to this, since the impedance in the reactorvaries in accordance with the condition of the reactor, namely, from thevacuum to the plasma, it is substantially impossible to provide a systemwhich results in satisfactory matching in both conditions of the vacuumand plasma.

In the illustrated apparatus, the dielectric constant (ε₁) inside thewaveguide 13 is 1, since air occupies the waveguide 13. Further, thedielectric constant (ε₃) inside the reactor 14, before the plasma isproduced therein, is 1. This is because the reactor 14 is maintained ata vacuum condition. The dielectric constant (ε₂) of the microwavetransmission window 10 depends on the type of the insulating materialused. For example, the dielectric constant (ε₂) of a silica window 10 isof the order of 3, and that of a ceramic window 10 is of the order of 9.Accordingly, in the two interfaces of the window 10 discussed above,there is a relationship of the dielectric constants ε₃ <ε₂ <ε₁.

Under the above relationship of dielectric constants, in order to attainappropriate matching or minimum reflection (R₁ +R₂) of the microwave, itis required to control the difference in reflection (R₁ -R₂) so that itequals ##EQU1## wherein λ is the wavelength of the microwaves, namely,odd times of λ/2, so that a phase shift or difference of half awavelength or λ/2 results between the phase of R₁ and that of R₂. R₁ andR₂ were previously described. It is, therefore, conventionally carriedout to adjust a thickness of the window 10 to λ/4.

The appropriate matching, however, is destroyed when the plasma is thenproduced in the reactor 14, whereby the relationship of the dielectricconstants is changed to ε₃ >ε₂ >ε₁. In this state, the maximumreflection (R₁ +R₂) of the microwaves is caused, as a result of thephase shift of one wavelength λ in total. In other words, if matching ispreviously obtained while the reactor is under vacuum, such matchingcannot be maintained during and after the plasma is produced in thereactor, because, as described above, the reflection of the microwave isincreased with the production of the plasma. Further, the inappropriatematching results in unsatisfactory production of the plasma, and thesudden and large reflection of the microwaves damages the apparatus orsystem. In practice, it has been observed from our experiments usingoxygen (O₂) as a reactive gas and a vacuum of 1 Torr that the reflectionof the microwaves was 70% (without matching) and 30% (with matching).

Another problem is decay of the microwaves in the reactor. Themicrowaves incident on the reactor, when the plasma is contained in thereactor, rapidly decay upon introduction into the reactor. In addition,the density of the plasma in the reactor decreases with the decay of themicrowaves. Accordingly, in order to attain uniform processing of theobject or material in the plasma, it is necessary to dispose the objectin the neighborhood of and parallel to the microwave transmissionwindow. This disposition is illustrated in FIG. 3, referring toreference number 8 (the disposition of the object illustrated byreference number 28 must be avoided).

In addition, there is a problem concerning the distance between thewindow and the stage on which the object is supported (see the referencesymbol . ."l".!. .Iadd."l" .Iaddend.in FIG. 4). When the object has anelectrical conductivity or when the stage is of a metallic material, thestrength of the microwave electric field is lowest at an interfacebetween the object and the stage. This means that, in the aboveinstance, it becomes difficult to attain effective production of theplasma independent of the distance . .(l).!. (.Iadd.l) .Iaddend.of thestage from the window. Therefore, hereinbefore, a long distance ..(l).!. (.Iadd.l) .Iaddend.has been set so that the the stage can bepositioned where the microwave electric field is maximum in strength. Ithas been observed that when the distance . .(l).!. (.Iadd.l) .Iaddend.isless than λ/4, no effective production of the plasma is attained, while,when the distance . .(l).!. (.Iadd.l) .Iaddend.is greater than λ/4, aremarkable decay of the plasma density at the neighborhood of the stageis caused at a pressure of 1 Torr or more. Our experiments using as areactive gas oxygen (O₂), which produces radicals having a short life,indicated that no resist material was ashed at a pressure of 4 Torr andthe distance . .(l).!. (.Iadd.l) .Iaddend.of 2 cm and that, at apressure of 1 Torr and the distance . .(l).!. (.Iadd.l) .Iaddend.of 4cm, the resist material was ashed, but its ashing rate was slow. Inaddition, it should be noted that the prior art generally recognizes acontradictory phenomenon that, in the ashing process of resist materialusing oxygen, the ashing can be attained only if the object is close tothe window, while an increase of the efficiency of the plasma processingcan be attained only if the distance . .(l).!. (.Iadd.l).Iaddend.between the window and the stage is long.

Further, there are problems in connection with the disposition of theobject. For example, it is difficult to dispose a cooling means for themetallic stage in the reactor and to reduce the size of the apparatus.

An example of a microwave plasma processing apparatus according to thepresent invention is illustrated in FIG. 5. A waveguide is indicatedwith reference number 30, through which the microwave produced in aconventional microwave generator 39 is transmitted in the direction ofthe arrow. A microwave transmission window 31 of an insulating materialsuch as silica or ceramic defines a part of the waveguide 30 andseparates a reactor or vacuum chamber 32 from the microwave transmissionregion of the waveguide 30. The reactor 32, as is shown in FIG. 5, isprovided with a reactive gas inlet 35, an evacuation outlet 36 connectedwith a conventional evacuation system (not shown), and a stage orsusceptor 34 on which an object or material . .to processed.!. .Iadd.tobe processed .Iaddend.33, for example, a semiconductor wafer, is laid.The object 33 is disposed parallel to the window 31.

As is apparent from FIG. 5, the microwave transmission window 31 isdisposed perpendicular to the direction (arrow 40) of the electric fieldof the progressive microwaves in the waveguide. In other words, thewindow 31 is parallel to the direction of the progressive microwaves.Namely, the direction of the window 31 is shifted 90° from that of thewindow 10 in the conventional perpendicular incidence-type plasmaetching apparatus shown in FIG. 3, for example. As a result, the mode ofthe microwaves traveling from the waveguide 30 to the reactor 32 is notadversely affected, and the microwaves are effectively absorbed into thereactor 32. Therefore, in the illustrated plasma processing apparatus,it has been found that matching can be easily accomplished.

In order to verify the above effects, we produced a microwave plasmaprocessing apparatus of the illustrated structure in which the microwavetransmission window 31 was formed from silica and had a thickness of 12mm. The distance (d) between the window 31 and the stage 34 was 3 mm.The distance (D) between the upper wall of the waveguide 30 and thestage 34 (a total of the height of the waveguide 30 in the direction ofthe electric field of the microwaves, the thickness of the window 31,and the distance (d) described above; the distance (D) hereinafter isalso referred to as "chamber height") was 50 mm. The resulting apparatuswas very small in comparison with the prior art perpendicularincidence-type apparatus. Microwaves having a frequency of 2.45 GHz,supplied from a microwave generator (not shown), were transmittedthrough the waveguide 30. Three hundred cc of oxygen gas . .was.!..Iadd.were .Iaddend.introduced through the inlet 35 into the reactor 32.Applying a vacuum of 0.3 Torr and an output power of 1.5 kW, plasmaetching was carried out to remove the resist material on the object 33(silicon wafer). The results gave an etching rate about five timeshigher than that of the prior art plasma etching process.

In connection with the above results, it has been found from ..our-further.!. .Iadd.our further .Iaddend.experiments that, in theoxygen plasma etching process at a vacuum of 1 Torr, the reflection ofthe microwaves is 30% (70% in the prior art process) when no matching ismade and 5% (30% in the prior art process) when matching is made. Such areduction of the reflection of the microwave enables a higher etchingrate.

In the illustrated apparatus of the present invention, it is easy todispose a cooling means in the apparatus, since the lower portion of thestage 34 does not have to be maintained in a vacuum condition. In fact,according to the present invention, it is possible to carry out theplasma processing at a temperature of 100° C. or less. It should benoted that, during the plasma processing, the object 33 is generallyheated to a higher temperature exceeding 200° C. if the apparatus has nocooling means.

In the practice of the present invention, it is preferred that thedimensions of the object or material to be processed be smaller thanthose of the microwave transmission window. This is because, when themicrowaves transmitted through the window are incident on the materialthey must cover all of the material. This enables uniform plasmaprocessing under limited plasma generating conditions.

Moreover, the distance or chamber height (D) discussed above ispreferred to be less than λ/2, wherein λ is the wavelength of themicrowaves. It has been found that such a chamber height results inreduction of the deflection of the reflected wave in the presence of theplasma, thereby extending the possible matching range. Further, when thechamber height (D) is less than λ/2, a tuning operation can be easilycarried out.

Further, while not illustrated in any of the accompanying drawings, itis preferred that the microwave transmission window be supported with aholder which is fitted to the waveguide and be replaceable. If thewindow is replaceable, it is easy to change the size and material of thewindow depending upon the conditions of the plasma processing. Further,an apparatus of this structure can be commonly used for both plasmaprocessing and after-glow discharge processing, for example. This meansthat the apparatus of the present invention can be widely used invarious different processes.

FIG. 6 illustrates an embodiment of the apparatus according to thepresent invention. As is illustrated, the height (L in FIG. 5) of thewaveguide 30 in the direction of the electric field of the microwaves isdecreased in the direction of travel of the microwaves. For example, theheight (L₂) is smaller than the height (L₁). FIG. 7 is a perspectiveview of the apparatus shown in FIG. 6.

Similarly, in the apparatus of FIG. 8, which is a modification of theapparatus of FIG. 6, the height of the waveguide is gradually decreasedso that the height (L₂) of the waveguide 30 is smaller than the height(L₁) of the same. FIG. 9 is a perspective view of the apparatus shown inFIG. 8.

In any case, when the height of the waveguide 30 is gradually decreasedin the manner shown, for example, in FIGS. 6 to 9, it effectivelycompensates for the loss of the strength of the electric field at an endportion of the waveguide 30. As a result of the decrease of thewaveguide height, a constant distribution of the strength of theelectric field in the waveguide 30 is provided, and reduction of thereflection of the microwaves therefore results. For example, we couldreduce the reflection power of the processing apparatus using anincident power of 1500 W from 400 W (prior art) to 150 W (presentinvention).

In the practice of the present invention, the microwave transmissionwindow generally comprises a disc-shaped element of an insulatingmaterial such as silica or ceramic. However, as an alternative, it may ..comprises.!. .Iadd.comprise .Iaddend.two or more rectangular, forexample, stripe-shaped, elements which are parallel to each other, thedistance between the two adjacent elements being λg/4, wherein λg is thewavelength of the microwaves in the waveguide. See FIG. 10. FIG. 11 is aperspective view of the apparatus of FIG. 10, in which 37a and 37b arenotches. The separation of the window into two or more elements in theillustrated manner is effective to prevent the breakage of the windowwithout narrowing the plasma area, when a window of a weak material suchas alumina is subjected to atmospheric pressure. This is because theopenings 37a and 37b act as an additional waveguide.

Finally, FIG. 12 shows that a stage 34 reciprocatable in the directionof the electric field of the progressive microwaves in the waveguide 30.The reciprocatable stage 34 is effective to control the distance (d)between the window 31 and the stage 34 depending upon various factors,such as conditions of the object 33 or the objects of the processing,thereby preventing damage of the object 33. It has been found that, inoxygen plasma processing for removing resist material from an aluminumsubstrate, at 0.3 Torr, the aluminum substrate was damaged at a distance(d) of 5 mm, but was not damaged at a distance (d) of 20 mm.

We claim:
 1. A microwave plasma processing apparatus for processing amaterial, comprising:a reaction gas source for supplying a reaction gas;a microwave generator generating microwaves having a wavelength λ; awaveguide, connected with said microwave generator, having a rectangularprism shape with a longitudinal axis and side-walls extending inparallel to the longitudinal axis, said waveguide receiving themicrowaves propagating in a first direction parallel to the side-wallsand for transferring the microwaves along the longitudinal axis of saidwaveguide; a dielectric window, formed of at least two rectangularelements parallel to each other, superposed over an opening in a firstside-wall of said waveguide, for transmitting the microwavestherethrough to an exterior surface thereof, the distance between thetwo rectangular elements being λg/4, where λg is a wavelength of themicrowaves in the waveguide; a plasma processing chamber connected tosaid reaction gas source and formed adjacent to the first side-wall ofsaid waveguide to entirely enclose the exterior surface of saiddielectric window, said plasma processing chamber offset on the exteriorof said waveguide from the first side-wall of said waveguide in a seconddirection perpendicular to the longitudinal axis of said waveguide, saidplasma processing chamber receiving the microwaves transmitted throughsaid dielectric window and the reaction gas supplied from said reactiongas source to generate plasma therein; and a stage for holding thematerial to be processed thereon, said stage disposed in said plasmaprocessing chamber with a top surface of said stage substantially inparallel with said dielectric window. .Iadd.
 2. A microwave plasmaprocessing apparatus in which material is to be processed usingmicrowaves received by said microwave plasma processing apparatus,comprising:a reactor for plasma processing therein, having a stage forholding the material to be processed; a waveguide for transferring themicrowaves in a propagating direction within the waveguide; and adielectric window, having first and second surfaces substantiallyparallel with the propagating direction of the microwaves adjacent saiddielectric window, said first surface formed coplanar with an innersurface of said waveguide and said second surface forming part of aninner surface of said reactor..Iaddend..Iadd.3. A microwave plasmaprocessing apparatus according to claim 2, wherein said dielectricwindow comprises insulating material, selected from at least one ofsilica and ceramic and alumina..Iaddend..Iadd.4. A microwave plasmaprocessing apparatus according to claim 2, further comprising amicrowave transmitter, disposed adjacent said reactor, to propagatemicrowaves in the direction of propagating microwaves, said microwavetransmitter having a first dielectric constant, wherein said reactor hasan interior with a second dielectric constant, and wherein saiddielectric window comprises a material having a third dielectricconstant with a value between the first and second dielectricconstants..Iaddend..Iadd.5. A microwave plasma processing apparatusaccording to claim 4, wherein said dielectric window comprises materialselected from a group of silica and ceramic..Iaddend..Iadd.6. Amicrowave plasma processing apparatus according to claim 2, wherein saiddielectric window comprises a disc-shaped element..Iaddend..Iadd.7. Amicrowave plasma processing apparatus according to claim 2, wherein saiddielectric window comprises plural windows, each of which has a sizesmall enough to prevent arising breakage in said plasmaprocessing..Iaddend..Iadd.8. A microwave plasma processing apparatusaccording to claim 7, wherein each of said plural windows is made ofalumina..Iaddend..Iadd.9. A microwave plasma processing apparatusaccording to claim 2, wherein said reactor further includes a reactivegas inlet and an exhaust gas outlet..Iaddend..Iadd.10. A microwaveplasma processing apparatus according to claim 2, wherein the surface ofthe material to be processed has dimensions smaller than said dielectricwindow..Iaddend..Iadd.11. A microwave plasma processing apparatusaccording to claim 2, wherein the microwaves have a wavelength λ,whereinsaid microwave plasma processing apparatus further comprises a microwavetransmitter, disposed adjacent said reactor, to propagate microwaves inthe direction of propagating microwaves, and wherein said stage has atop surface supporting the material to be processed and separated froman opposing wall of said microwave transmitter opposite said dielectricwindow by a distance of less than λ/2 during processing of thematerial..Iaddend..Iadd.12. A microwave plasma processing apparatusaccording to claim 2, further comprising a microwave transmitter,disposed adjacent said reactor, propagating microwaves in the directionof propagating microwaves and having a height, measured perpendicular tosaid dielectric window, gradually decreasing from a first value abovesaid dielectric window to a second value at an end wall of saidmicrowave transmitter downstream from said dielectricwindow..Iaddend..Iadd.13. A microwave plasma processing apparatusaccording to claim 2, further comprising: a microwave transmitter,disposed adjacent said reactor, to propagate microwaves in the directionof propagating microwaves; and a holder, supporting said dielectricwindow, replaceably fitted to said microwavetransmitter..Iaddend..Iadd.14. A method for processing a material byplasma, comprising: placing the material in a chamber having adielectric window disposed in substantially the same plane as an innersurface of a waveguide; and introducing microwaves via the waveguidealong a first direction, substantially parallel to the inner surface ofthe waveguide and along the dielectric window, so that the plasma isgenerated in the chamber..Iaddend..Iadd.15. A microwave plasmaprocessing method according to claim 14, wherein the dielectric windowcomprises insulating material, selected from at least one of silica andceramic and alumina..Iaddend..Iadd.16. A microwave plasma processingmethod according to claim 14,further comprising transmitting themicrowaves within a microwave transmitter in a direction of microwavepropagation, wherein the microwave transmitter and the reactor haveinteriors with first and second dielectric constants, respectively, andwherein the dielectric window comprises a material having a thirddielectric constant with a value between the first and second dielectricconstants..Iaddend..Iadd.17. A microwave plasma processing methodaccording to claim 16, wherein the dielectric window comprises materialselected from a group of silica and ceramic..Iaddend..Iadd.18. Amicrowave plasma processing method according to claim 14, wherein thedielectric window comprises disc-shaped element..Iaddend..Iadd.19. Amicrowave plasma processing method according to claim 14, wherein thedielectric window comprises plural windows, each of which has a sizesmall enough to prevent arising breakage in said plasmaprocessing..Iaddend..Iadd.20. A microwave plasma processing methodaccording to claim 19, wherein each of the plural windows is made ofalumina..Iaddend..Iadd.21. A microwave plasma processing methodaccording to claim 14, wherein the reactor includes a reactive gas inletand an exhaust gas outlet..Iaddend..Iadd.22. A microwave plasmaprocessing method according to claim 14,further comprising the step oftransmitting the microwaves within a microwave transmitter in adirection of microwave propagation, and wherein the microwaves have awavelength λ, and the stage has a top surface supporting the material tobe processed and separated from an opposing wall of the microwavetransmitter opposite the dielectric window by a distance of less thanλ/2 during said generating of the plasma..Iaddend..Iadd.23. A microwaveplasma processing method according to claim 14, further comprising thestep of transmitting the microwaves within a microwave transmitter in adirection of microwave propagation, and wherein the microwavetransmitter has a height, measured perpendicular to the dielectricwindow, gradually decreasing from a first value above the dielectricwindow to a second value at an end wall of the microwave transmitterdownstream from the dielectric window..Iaddend..Iadd.24. A method forfabricating an integrated circuit semiconductor device,comprising:transmitting microwaves within a microwave transmitter havingan inner surface in a plane substantially parallel to a direction ofmicrowave propagation; disposing on a stage inside a reactor asemiconductor wafer having a surface substantially parallel to thedirection of microwave propagation, with at least one of photoresistfilms to be removed from and protective layers to be etched off thesurface of the semiconductor wafer; reducing pressure in the reactorsufficiently to permit generation of plasma; and generating the plasmaby transmitting the microwaves through a dielectric window, having afirst surface in substantially the plane of the inner surface of themicrowave transmitter and thereby, parallel to the direction ofmicrowave propagation adjacent the dielectric window, without alteringthe direction of microwave propagation in the microwavetransmitter..Iaddend..Iadd.25. A microwave plasma processing methodaccording to claim 24, further comprising cooling the material to beprocessed on the stage using a cooler, disposed below the stage, duringat least said generating of the plasma..Iaddend..Iadd.26. A microwaveplasma processing apparatus for processing material therein, comprising:a reactor for plasma processing therein, having a stage for holding thematerial to be processed; a waveguide for transferring microwaves; and adielectric window, disposed between said reactor and said waveguide insubstantially the same plane as an inner surface of said waveguide andthereby substantially parallel with a direction of propagation of themicrowaves adjacent the dielectric window..Iaddend..Iadd.27. Anapparatus for processing a material by plasma comprising:a chamberhaving a dielectric window and a stage for placing the material; agenerator for generating microwaves; and a waveguide for introducing themicrowaves from the generator to the chamber, wherein the dielectricwindow is disposed in substantially the same plane as an inner surfaceof said waveguide and thereby substantially parallel to a directionalong which the microwaves propagate adjacent the dielectric window sothat the plasma is generated in said chamber..Iaddend..Iadd.28. A methodfor processing a material by plasma, comprising: placing the material ina chamber having a dielectric window; and introducing a microwave alonga waveguide in a first direction adjacent the dielectric windowsubstantially in parallel with an outer surface of the dielectric windowdisposed in substantially the same plane as an inner surface of thewaveguide, so that the plasma is generated in thechamber..Iaddend..Iadd.29. A microwave plasma processing method forprocessing a material with microwave generated plasma,comprising:disposing the material to be processed on a stage inside areactor, and positioning the stage facing a dielectric window formed asa part of the reactor; and introducing microwaves along a waveguidehaving an inner surface in a plane, the dielectric window being disposedwith an outer surface substantially in the plane of the inner surface ofthe waveguide, with the microwaves thereby propagating adjacent thedielectric window in a direction parallel to the dielectric window, soas to generate plasma between the dielectric window and thestage..Iaddend..Iadd.30. A microwave plasma processing apparatus toprocess material therein, comprising: a microwave transmitter topropagate microwaves in a direction of microwave propagation insidecontainment walls, each having an inner surface; a reactor having astage to hold the material to be processed with a surface of thematerial substantially parallel to the direction of microwavepropagation; and a dielectric window, disposed with a first surface insubstantially a same plane as the inner surface of one of thecontainment walls of the microwave transmitter and thereby substantiallyparallel to the direction of microwave propagation adjacent thedielectric window, and a second surface substantially parallel to thefirst surface, to provide a pressure seal between said microwavetransmitter and said reactor enabling generation of a plasma inside saidreactor..Iaddend..Iadd.31. A microwave plasma processing apparatus inwhich material is to be processed therein, comprising:a reactor forplasma processing therein, having a stage for holding the material to beprocessed; a waveguide for transferring microwaves; and a dielectricwindow, disposed so as to be part of a surface of said reactor and besubstantially on the same plane as an inner surface of said waveguide,and thereby substantially parallel with a direction of propagatingmicrowaves..Iaddend.